Hector Garcia-Gonzalez

Underground mining environments present elevated occupational health risks, primarily due to substantial exposure to diesel exhaust emissions within confined and poorly ventilated spaces. This study assesses the real-world performance of two advanced retrofit emission control systems—Proventia NOxBuster and Purifilter—installed on underground mining trucks operating in a Spanish mine. Emissions of carbon monoxide (CO), nitric oxide (NO), and nitrogen dioxide (NO₂) were quantified using a Testo 350 multigas analyser, while ultrafine particle (UFP) concentrations were measured with an Engine Exhaust Particle Sizer (EEPS-3090) equipped with a thermodiluter. Controlled tests under both idling and acceleration conditions revealed substantial reductions in pollutant emissions: CO decreased by 60–98%, NO by 51–92%, and NO₂ by 20–87%, depending on the system and operational phase. UFP concentrations during idling dropped by approximately 90%, from 542,000 particles/cm³ in untreated trucks to below 50,000 particles/cm³ in retrofitted vehicles. Under acceleration, the Proventia NOxBuster achieved reductions exceeding 95%. Conversely, Purifilter-equipped trucks exhibited a counterintuitive increase in UFPs within the 5.6–40 nm range, potentially due to ammonia slip events during selective catalytic reduction (SCR). Despite these discrepancies, both systems demonstrated considerable mitigation potential, albeit highly dependent on exhaust temperature (optimal: 200–450 °C), urea dosing precision, and maintenance protocols. This work underscores the necessity of in situ performance verification, regulatory vigilance, and targeted intervention strategies to protect underground workers effectively. Further investigation is warranted into the long-term health benefits, system durability, and nanoparticle emission dynamics under variable load conditions.

Diesel-powered machinery is the primary energy source in underground mining, exposing workers to hazardous diesel exhaust emissions. This study evaluates occupational exposure to diesel particulate matter (DPM) and gaseous pollutants (NO, NO₂) at an underground mine before and after implementing Diesel Particulate Filters (DPF) and Selective Catalytic Reduction (SCR) in mining equipment. A comprehensive monitoring campaign was conducted, employing elemental carbon (EC) as a tracer for diesel particulate emissions and electrochemical sensors for gas measurements. Results show a substantial reduction in EC concentrations following the implementation of DPFs, with median EC exposure decreasing from 0.145 mg/m³ in 2021 to 0.034 mg/m³ in 2023, and the proportion of samples exceeding the occupational exposure limit (OEL) falling from 90% to 28%. Similarly, SCR implementation led to a 72% reduction in NO₂ levels and a 77.5% decrease in NO concentrations in certain equipment; however, NO levels remained persistently high near loaders, suggesting that additional mitigation measures are required. These findings underscore the efficacy of DPF and SCR technologies in improving air quality and reducing occupational exposure in underground mining environments. Nevertheless, persistent NO concentrations and maintenance-related challenges highlight the need for a holistic emission control approach, integrating ventilation improvements, expanded DPF adoption, alternative propulsion systems, and enhanced maintenance protocols. This study provides critical insights into the effectiveness of advanced emission reduction strategies and informs future regulatory compliance efforts in the mining industry.

This study provides a comprehensive analysis of volatile organic compound (VOC) emissions in the context of 3D printing, a rapidly advancing technology that is transforming manufacturing processes. As the adoption of 3D printing grows, concerns regarding its potential impact on indoor air quality have emerged. This research addresses these concerns by investigating the risks associated with VOC emissions and proposing effective mitigation strategies. Using a robust methodology, filament and resin-based 3D printers were employed alongside VOC sampling equipment (Tenax tubes and personal pumps) to assess emissions. A detailed analysis of 49 VOCs revealed variable concentrations across different printing materials, with ethyl acetate being the dominant compound in resin printing and decanal in filament printing. While individual VOC levels were below 1% of occupational exposure limits, total VOC concentrations frequently exceeded the recommended indoor threshold of 200 µg/m³, particularly in resin-based processes. This raises concerns about the combined effects of multiple VOCs, some of which are known carcinogens. These findings underscore the need for further investigation into the cumulative health impacts of prolonged exposure to multiple VOCs. The study also emphasises the importance of accounting for both facility-specific conditions and material emissions to fully understand the environmental and health consequences of 3D printing. Preventative measures, such as enclosing 3D printers and equipping them with extraction systems, are recommended to safeguard user health.

This study investigates the environmental and occupational health risks associated with arsenic (As) and mercury (Hg) contamination in a specific industrial site: a mercury mine site that contains a metallurgical plant within its premises. Utilising a comprehensive sampling and analysis approach, As and Hg concentrations in the soil and air across various zones within the site were assessed. The results revealed elevated levels of both contaminants, particularly in areas proximal to industrial processes such as metal smelting and waste disposal. Risk assessment using the Cancer Risk (CR) and Hazard Index (HI) indices demonstrated significant health hazards that exceed regulatory thresholds, indicating potential carcinogenic effects from As exposure and risks of non-cancerous occupational diseases. Three distinct risk areas were identified based on the CR and HI indices, guiding the formulation of tailored risk management strategies. While some zones may permit limited industrial activities under specific conditions, others require stringent safety measures and specialised personal protective equipment (PPE) due to exceptionally high contaminant concentrations. Overall, the findings underscore the critical need for robust safety protocols and regulatory compliance to mitigate the health risks associated with As and Hg exposure in industrial settings, ensuring the protection of worker health, environmental stewardship, and the promotion of sustainable mining practices.

This study investigates nanoparticle emission during 3D printing processes, assessing various filament materials’ impact on air quality. Commonly used 3D printers, including both filament and resin-based types, were examined. The study’s scope encompasses diverse filament materials like ABS (acrylonitrile butadiene styrene), PLA (polylactic acid), PETG (polyethylene terephthalate glycol), ASA (acrylonitrile styrene acrylate), TPU (thermoplastic polyurethane), PP (polypropylene), nylon, and wood-based variants, alongside three types of resins. The research delves into the relationship between the type of material and nanoparticle emissions, emphasizing temperature’s pivotal role. Measurement instruments were employed for nanoparticle quantification, including an engine exhaust particle sizer spectrometer, condensation particle counter, and nanozen dust counters. Notably, results reveal substantial variations in nanoparticle emissions among different filament materials, with ASA, TPU, PP, and ABS showing considerably elevated emission levels and characteristic particle size distribution patterns. The findings prompt practical recommendations for reducing nanoparticle exposure, emphasizing printer confinement, material selection, and adequate ventilation. This study offers insights into potential health risks associated with 3D printing emissions and provides a basis for adopting preventive measures.

Environmental air pollution poses a significant threat to human health, with nitrogen oxides (NOx) identified as contributors to respiratory and cardiovascular diseases. This study evaluates NOx levels in an underground car park of a hospital complex, where vulnerable patients frequently visit. NOx levels were assessed using direct-reading devices with high-resolution electrochemical sensors measuring NO and NO₂ concentrations. Measurements consistently remained below the legal occupational exposure limit values for car park employees, averaging around 10% of the limit. However, approximately 75% of days recorded NO₂ concentrations exceeding 70% of the World Health Organization’s (WHO) recommendations, with about 20% surpassing the 0.1 ppm limit set by the WHO. The highest recorded one-hour NO₂ level reached 0.165 ppm, typically around 11:00 h. The study recommends that vulnerable patients, especially asthmatics, utilize outdoor parking, while all users should avoid using the car park as a waiting area. Employees are advised to spend more time in enclosed spaces with fresh air. Although occupational levels are generally within limits, environmental levels during peak hours could pose risks to vulnerable populations. Mitigation measures, such as increased ventilation during peak hours and restricted access based on emission levels, are suggested to minimize exposure and protect public health.

The generation of CO₂ is an important element in assessing the environmental impact generated in a tunnel construction project, making this knowledge very useful for evaluating different alternatives. In this study, an analysis of the carbon footprint has been carried out, including the main elements during the construction phase of a tunnel employing a tunnel boring machine (TBM). The research proposes several options for an easy and quick calculation of CO₂ generation in a design phase. Its determination can be crucial for decision-making before and during the execution of any tunnel in the near future. The estimation models have been validated based on real case studies, defining the carbon footprint of each construction element. The proposed procedure can apply to any tunnel. However, it should be noted that it is an approximate analysis, and the limitations described in each section should be considered. The main CO₂ generator found in the construction process is the lining element; the percentage varies between 50% in tunnels with smaller diameters (4–5 m) and 75% for tunnels with larger diameters (9–10 m), followed by the auxiliary elements, 16%, and the operation of the tunnel boring machine itself, 11.2%, while the other parts remain in a range between 1.3 and 5.7%. This knowledge makes it possible to define the aspects on which efforts should be focussed to reduce the carbon footprint of the tunnel construction process.

The definition of a rock mass’s characteristics is crucial in underground construction to avoid delays and cost overruns. This study proposes a system to quantify the economic uncertainty related to a lack of knowledge of a rock mass in the tunnel construction stage, either for tunnel boring machines or for drill and blast excavation techniques. Using a back-analysis of three actual tunnels completed in Spain (Burata, Lot 3 of the Pajares variant, and Bolaños), the study assessed the directional core drilling technique (DCD) for this purpose, comparing it with conventional boreholes. In this regard, the DCD approach reduced the uncertainty by between EUR 6.7 and EUR 12.7 for every EUR 1, while the total cost of the drilling campaign remained within a widely accepted proportion of the construction budget. Overall, the uncertainty was reduced by approximately EUR 6000 per meter of the tunnel.

Directive 2017/164/EU proposed a drastic reduction of nitrogen monoxide (NO) and nitrogen dioxide (NO₂) levels, thereby fortifying the health protection framework within the mining industry. Despite the commendable record of non-road emissions standards (Stage IV and V) in continuing to reduce NOx emissions, concerns remain about compliance with the directive’s strict limits, particularly in demanding tunnels and mining fields. To illustrate this problem, this study undertakes a comprehensive assessment of the practical feasibility surrounding the implementation of these proposed limits in a 6.2 internal diameter tunnel-boring machine (TBM) tunnel constructed with Stage III emission locomotives. The results cast light upon the formidable challenges entailed in achieving strict compliance with the envisioned limits, with a substantial number of measurements notably surpassing these thresholds, primarily concerning NO₂ emissions from Stage III engines. To address these challenges, this study highlights the key role of moving to Stage IV-V locomotives or introducing electric locomotives to effectively reduce NOx emissions, ensure compliance with the directive, and avoid delays in tunnel construction.